Direct Imaging and Astrometric Detection of a Gas Giant Planet Orbiting an Accelerating Star

TL;DR

This study combines Gaia and Hipparcos astrometry with direct imaging to discover and confirm a gas giant exoplanet orbiting HIP 99770, providing insights into planetary atmospheres and system architectures.

Contribution

It demonstrates a novel approach of integrating astrometric data with direct imaging to detect and confirm exoplanets around nearby stars.

Findings

Discovered a gas giant planet at 17 AU from HIP 99770.

Confirmed the planet through direct imaging with Subaru.

Planet's atmosphere resembles an older, less-cloudy version of known exoplanets.

Abstract

Direct imaging of gas giant exoplanets provides key information on planetary atmospheres and the architectures of planetary systems. However, few planets have been detected in blind surveys used to achieve imaging detections. Using Gaia and Hipparcos astrometry we identified dynamical evidence for a gas giant planet around the nearby star HIP 99770 and then confirmed this planet by direct imaging with the Subaru Coronagraphic Extreme Adaptive Optics Project. HIP 99770 b orbits 17 astronomical units from its host star, with an insolation comparable to Jupiter's and a dynamical mass of 13.9--16.1 Jupiter masses. Its planet-to-star mass ratio (7--8$\times$10$^{-3}$) is comparable to that other directly-imaged planets. The planet's atmosphere resembles an older, less-cloudy analogue of the atmospheres of previously-imaged exoplanets around HR 8799.